The present invention relates generally to medical equipment and, more specifically, to filters and filter devices for use in medical injection and infusion equipment, such as hypodermic needles and intravenous infusion sets, and to methods of making such filters and filter devices.
In recent years medical researchers have been expressing increasing concern about the presence of particulate contamination in parenteral solutions intravascularly infused or injected into patients, and about the possible harm such contamination may cause. The term "parenteral solutions" as used throughout this patent is intended to refer to any solution intravenously or intramuscularly fed to a patient, including medication injected by a hypodermic syringe and various solutions (e.g., glucose, blood, medication, etc.) fed intravenously through an inravenous infusion set.
It is estimated that the average hospital patient currently receives approximately 2.5 liters of parenteral solutions during his illness, and the critically ill patient may receive as much as 100 liters or more. Recent studies have shown that the parenteral solutions are often comtaminated by particulate matter from the infusion equipment, e.g., the glass or plastic container for the solution, the tubing set, the stopper or "bung" and other accessories of the equipment. Obviously such contamination may be harmful to the patient, depending on the type, size, quantity, etc., of the contaminating particles. Harmful effects have been demonstrated by medical researchers by means of human autopsies and studies on various animals.
Particulate contamination is also present in the parenteral solutions injected into patients by means of hypodermic syringes. Sources of such contamination include the syringe barrels, plungers (which typically have rubber tips) and the covers (typically rubber) and interior (typically glass) of multi-dose vials from which solutions to be injected are withdrawn.
It is thus apparent that there is a need in the medical field for some means to prevent or minimize particulate matter contamination in parenteral solutions infused or injected into patients.